Rockwell Automation 1785-CHBM ControlNet PLC-5 Hot Backup System User Manual - Manual (Page 107)

Publication 1785-UM024B-EN-P - January 2003
Data Table Crossloading C-9
Effect of Data Table Crossloading on the ControlNet Channel
Data table crossloading only transfers one file at a time. Also, only one
unscheduled buffer is used at any one time. So the impact of the data
table crossloading on available ControlNet channel unscheduled
bandwidth should be minimal. Also, the impact of data table
crossloading on the available unscheduled buffers is minimal.
Note: When you use Data Highway Plus crossloading, it does not
impact the ControlNet channel unscheduled bandwidth.
Inhibiting Data Table Crossloads
All crossloading is inhibited if there is any difference at all in the data
table structures between the two processors. This inhibits all data
table crossloads, not just data table crossloads to files whose structures
differ between the two systems.
You can make the data table structures differ between the two systems
by creating an extra data table file on one of the systems, or by
increasing the size of one of the data table files.
For a qualified backup system, you are given an indication as to
whether the data table structures match in the Equivalence Check
Error word (word 49 of the ControlNet Backup Integer File) bit 1.
You can ensure that the qualifying system fails qualification and major
faults if the data table structures do not match by enabling data table
Equivalence checking.
Data Table Crossload Diagnostics
There are some words reserved in the ControlNet Backup Integer File
for data table crossload diagnostics. First, there is a data table
crossload active word (word 52 in the ControlNet Backup Integer file).
This word is non-zero whenever a data table crossload is active.
This word is zero whenever a data table crossload is inactive.
When a data table crossload fails, diagnostic information is stored in 2
words of the ControlNet Hot Backup Integer (CHBI) file. Word 54 of
the CHBI file contains the file number of the crossload that failed.
Word 53 of the CHBI file contains the error code indicating the reason
why the crossload failed.